West Virginia Attorney General Patrick Morrisey’s announcement he is running for a U.S. Senate seat should have come as no surprise, though U.S. Rep. Evan Jenkins. R-W.Va., no doubt had high hopes Morrisey would stay out of the race.

What Morrisey’s entry means, in a nutshell, is that if Mountain State Republicans are not very careful, they will hand re-election to incumbent Sen. Joe Manchin, D-W.Va., on a silver platter.

Manchin is in the enviable position of having no meaningful opposition from within his party and no reason to expect any. That means he can hold onto much of what his re-election campaign raises and spend it for the November 2018 general election, rather than before the primary next spring. It also means there will be little or no criticism of him by Democrats during the next several months.

The incumbent can count on relatively solid support from West Virginia Democrat voters for two reasons: First is that he is a Democrat and many voters in his party prefer a Democrat senator. Second is that Democrat voters sick of the national party’s liberal bent will be less likely to vote Republican because Manchin has cultivated a reputation of being much more conservative than many other senators in his party.

Heck, he seems to be on good terms with President Donald Trump. In West Virginia, that counts for a lot.

Manchin gets at least something of a reprieve from GOP criticism. Jenkins and Morrisey are both quality candidates, meaning they will have quite a battle between them leading up to the primary. Neither will be able to refrain entirely from criticizing the other and using scarce campaign dollars prior to May. That means the winner will have less to spend next summer and early fall in the campaign against Manchin.

Inevitably, the Morrisey-Jenkins duel will cost the winner votes in November 2018. Some loyal to each man will sit out the general election if their candidate loses the primary. Charges and counter-charges traded between the two will make it less likely that in the general election, Democrats will abandon Manchin to vote for a Republican.

Both Jenkins and Morrisey understand all this. Both remain confident for both the primary and the general election — though Jenkins’ strategy may have been based on his early entrance into the race several weeks ago. Clearly, he hoped to use a combination of persuasion and intimidation to keep Morrisey out.

That didn’t work. Morrisey has weighed the odds — and he’s very good at that — and decided he can overcome Jenkins, then whip Manchin.

Here are a few factors that will help determine who wins both the primary and the general election:

• First, Manchin is wildly popular in West Virginia. He was governor during a period when state finances were in such good shape that tax relief and paying down debt could be achieved. There’s no spending-cut tarnish to him.

• No one plays both sides of the fence better than the incumbent. He takes his cue on that from the late Sen. Robert Byrd, D-W.Va. Manchin appeals to both conservative Democrats and some Republicans. That’s a winning coalition.

• Negative campaigning will be a factor. Jenkins already is doing that against Morrisey. But so did Morrisey’s Democrat opponent, Doug Reynolds, in the attorney general’s race last year.